Yun et al. BMC Anesthesiology (2016) 16:57 DOI 10.1186/s12871-016-0220-3
RESEARCH ARTICLE
Open Access
Head elevation by 3 vs. 6 cm in ProSeal laryngeal mask airway insertion: a randomized controlled trial Mi-jung Yun1, Jung-Won Hwang2*, Sung-Hoon Kim1, Hyo-Ju Hong1, Young-Tae Jeon2 and Hee-Pyoung Park3
Abstract Background: The sniffing position (neck flexion by head elevation and head extension) is commonly used for insertion of a laryngeal mask airway. However, the appropriate degrees of head elevation and head extension are unclear. In the present study, the success rate of ProSeal™ laryngeal mask airway (LMA ProSeal) insertion using two degrees of head elevation was evaluated. Methods: This prospective randomized, controlled study included 80 adult patients aged 18 to 90 years. In the 3 cm (n = 40) and 6 cm (n = 40) groups, the LMA ProSeal was inserted while the head was elevated 3 cm and 6 cm, respectively, using a pillow of the corresponding height. The success rate, and incidence of blood staining on cuff, sore throat and hoarseness were assessed. The alignments of laryngeal and oral axes were also evaluated. Results: The first attempt success rate was higher in the 3 cm than the 6 cm group (87 % vs. 60 %, P = 0.014). In 86 % of patients in the 6 cm group and 50 % of patients in the 3 cm group in whom the second attempt failed, the third insertion attempt was successful by using a pillow height of the opposite group. The alignments of the two axes were not different between the two groups (P > 0.05). Conclusions: The first attempt success rate of ProSeal laryngeal mask insertion was higher with 3 cm than 6 cm head elevation in adult patients. Trial registration: Identifiers: NCT02058030 (08/05/2015), Unique Protocol ID: phdkim1. Keywords: Airway, PLMA, LMA, Head position
Background Much effort has focused on determining the appropriate head and neck position for successful tracheal intubation. A radiologic study [1] reported that the anatomic sniffing position (neck flexion by head elevation and head extension with a pillow) provides greater occipitoatlanto-axial extension, compared to simple head extension (head extension without a pillow), suggesting the sniffing position to be optimal for laryngoscopy during endotracheal intubation. The standard for successful * Correspondence: [email protected] 2 Department of Anesthesiology and Pain Medicine, Seoul National University Bundang Hospital, College of Medicine, Seoul National University, Seongnam, Korea Full list of author information is available at the end of the article
endotracheal intubation is 35° of neck flexion and 15° of head extension [2]. Moreover, the head should be elevated 31–71 mm to get those angles during endotracheal intubation. For laryngeal mask airway (LMA) insertion, it is recommended to use a pillow for neck flexion [3]; however, the appropriate degree of neck flexion is unclear. The results of clinical studies of the influence of head and neck position on the success rate of LMA insertion differ from that of tracheal intubation. The first-attempt success rate of LMA insertion using a standard position (neck fully flexed and head fully extended) or a neutral position (head extended) was investigated [4]. In that study, the insertion success rate (100 % vs. 95 %) and fiber-optic laryngeal scores were not different between the two groups.
© 2016 Yun et al. Open Access This article is distributed under the terms of the Creative Commons Attribution 4.0 International License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution, and reproduction in any medium, provided you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. The Creative Commons Public Domain Dedication waiver (http://creativecommons.org/publicdomain/zero/1.0/) applies to the data made available in this article, unless otherwise stated.
Yun et al. BMC Anesthesiology (2016) 16:57
The first-attempt success rate of ProSeal™ LMA (PLMA) insertion and fiber-optic laryngeal score according to head position (sniffing, neck flexion and head extension by means of an 8-cm-high pillow vs. head extension without a pillow) and presence of a difficult airway were assessed [5]. The two factors (head position, difficult airway) had no influence on the first-attempt success rate of PLMA insertion and fiber-optic score in that study. In most clinical situations, with the exception of patients with cervical instability, the sniffing position has been used commonly, but the appropriate degree of head elevation has not been investigated thoroughly. The purpose of this study was to determine the pillow height (3 vs. 6 cm) that results in the highest success rate of LMA placement. The primary outcome variable was the success rate of PLMA insertion. The secondary outcome variables were blood on the surface of the PLMA cuff, postoperative sore throat and hoarseness as indices of complications.
Methods Patients and protocol
This prospective, single-center, randomized, single-blinded, parallel group comparison study was approved by the Institutional Review Board of the National Medical Center (authorization number H-1305/029-001). Written informed consents were obtained from all patients. This randomized controlled trial was registered at ClinicalTrials.gov (NCT02058030). Eighty adult patients (age range 18– 90 years; American Society of Anesthesiologists physical status 1–2) scheduled for minor surgery in the supine position were enrolled. The patients were recruited from November 2013 to November 2014. Patients were excluded if they had a known or predicted difficult airway, recent sore throat, mouth opening less than 2.5 cm, or risk of aspiration (non-fasted or gastroesophageal reflux disease). Anesthesiologists who did not perform the anesthesia enrolled the participants and assigned them to one of the two groups (3 cm group, 3 cm head elevation; 6 cm group, 6 cm head elevation), using a computer-generated randomization table (generated by Mi-Jung Yun at www.randomizer.org). The allocation ratio was 1:1. The assignment was concealed in an envelope until the start of anesthesia. Both patients and evaluators were blinded to the study. The standard anesthesia protocol was as follows: monitoring devices were connected before anesthetic induction; these included an electrocardiograph, pulse oximeter, gas analyzer and non-invasive blood pressure monitor. Anesthesia was induced with intravenous (IV) propofol (1–2 mg/kg) and inhalation of 6–8 vol% sevoflurane. Neuromuscular blockade was achieved with IV rocuronium (0.6 mg/kg). The patient’s head was elevated using a firm 3 cm pillow (3 cm group) or 6 cm pillow (6 cm group) and PLMA was inserted in the sniffing position.
Page 2 of 6
Anesthesia was maintained with 1.5–2.5 vol% sevoflurane in 50 % O2 and air. Water-based gel without a local anesthetic was applied to the posterior and lateral surface of the PLMA for lubrication, and the cuff was fully deflated before insertion. PLMA size was determined based on age and weight. Heart rate (HR) and mean blood pressure (MBP) were recorded 1 min before and 1 min after PLMA insertion. All insertions were performed by a single experienced PLMA user who was not blinded to the pillow height. The standard insertion technique was applied in both groups using an index finger, according to the manufacturer’s instructions [3]. The patient’s head was elevated with a pillow and the head was extended using the anesthesiologist’s non-dominant hand. The index finger of the dominant hand was placed in the retaining strap of the PLMA. The PLMA was pressed against the hard palate and advanced into the hypopharynx until resistance was felt. The laryngeal and oral axes were measured to assess their alignment. It was postulated that insertion would be more difficult with a greater difference in angle between the two axes and the PLMA would be more likely to buckle against the posterior pharyngeal wall. The laryngeal and oral axes were assessed using images obtained on the right side of the patient during PLMA insertion. A physician, who was blinded to the study, acquired the images while the pillow was covered using a barrier. The airway axes were defined as follows: angle of the ventral neck (an imaginary line along the long axis of the trachea) and the oral axis (an imaginary midline perpendicular to the line between the upper and lower lip). The angles were measured in images of all patients. Using a protractor, each angle was assessed three times by three individual anesthesiology residents, who were blinded to the study and could not determine pillow height on the images. The difference in angle of adjacent two axes was considered the alignment between the two axes. A lesser angle difference (oral axis - ventral neck angle) indicated greater alignment of the two airway axes (Fig. 1). The PLMA was connected to a breathing circuit after insertion, and the cuff was inflated with air until an effective airway was secured. An effective airway was defined as normal thoracoabdominal movement and a square-wave capnograph tracing. Airway pressure and end-tidal CO2 concentration were monitored. If insertion failed after two attempts using a pillow of the same height (head elevation), a third insertion trial was performed using a pillow height of the opposite group. If the third attempt was unsuccessful, it was regarded as a failure, and tracheal intubation was performed. The number of insertion attempts was recorded. Airway seal pressure was measured by setting the adjustable pressure limiting valve to 30 cmH2O and manually ventilating the
Yun et al. BMC Anesthesiology (2016) 16:57
Page 3 of 6
Fig. 1 Flow diagram generated in accordance with CONSORT 2010 guidelines
patient while listening with a stethoscope over the mouth [6] and epigastrium [7] to detect oropharyngeal and gastric air leaks, respectively. The PLMA was repositioned if air leaked up the drainage tube or if ventilation was ineffective (expired tidal volume
RESEARCH ARTICLE
Open Access
Head elevation by 3 vs. 6 cm in ProSeal laryngeal mask airway insertion: a randomized controlled trial Mi-jung Yun1, Jung-Won Hwang2*, Sung-Hoon Kim1, Hyo-Ju Hong1, Young-Tae Jeon2 and Hee-Pyoung Park3
Abstract Background: The sniffing position (neck flexion by head elevation and head extension) is commonly used for insertion of a laryngeal mask airway. However, the appropriate degrees of head elevation and head extension are unclear. In the present study, the success rate of ProSeal™ laryngeal mask airway (LMA ProSeal) insertion using two degrees of head elevation was evaluated. Methods: This prospective randomized, controlled study included 80 adult patients aged 18 to 90 years. In the 3 cm (n = 40) and 6 cm (n = 40) groups, the LMA ProSeal was inserted while the head was elevated 3 cm and 6 cm, respectively, using a pillow of the corresponding height. The success rate, and incidence of blood staining on cuff, sore throat and hoarseness were assessed. The alignments of laryngeal and oral axes were also evaluated. Results: The first attempt success rate was higher in the 3 cm than the 6 cm group (87 % vs. 60 %, P = 0.014). In 86 % of patients in the 6 cm group and 50 % of patients in the 3 cm group in whom the second attempt failed, the third insertion attempt was successful by using a pillow height of the opposite group. The alignments of the two axes were not different between the two groups (P > 0.05). Conclusions: The first attempt success rate of ProSeal laryngeal mask insertion was higher with 3 cm than 6 cm head elevation in adult patients. Trial registration: Identifiers: NCT02058030 (08/05/2015), Unique Protocol ID: phdkim1. Keywords: Airway, PLMA, LMA, Head position
Background Much effort has focused on determining the appropriate head and neck position for successful tracheal intubation. A radiologic study [1] reported that the anatomic sniffing position (neck flexion by head elevation and head extension with a pillow) provides greater occipitoatlanto-axial extension, compared to simple head extension (head extension without a pillow), suggesting the sniffing position to be optimal for laryngoscopy during endotracheal intubation. The standard for successful * Correspondence: [email protected] 2 Department of Anesthesiology and Pain Medicine, Seoul National University Bundang Hospital, College of Medicine, Seoul National University, Seongnam, Korea Full list of author information is available at the end of the article
endotracheal intubation is 35° of neck flexion and 15° of head extension [2]. Moreover, the head should be elevated 31–71 mm to get those angles during endotracheal intubation. For laryngeal mask airway (LMA) insertion, it is recommended to use a pillow for neck flexion [3]; however, the appropriate degree of neck flexion is unclear. The results of clinical studies of the influence of head and neck position on the success rate of LMA insertion differ from that of tracheal intubation. The first-attempt success rate of LMA insertion using a standard position (neck fully flexed and head fully extended) or a neutral position (head extended) was investigated [4]. In that study, the insertion success rate (100 % vs. 95 %) and fiber-optic laryngeal scores were not different between the two groups.
© 2016 Yun et al. Open Access This article is distributed under the terms of the Creative Commons Attribution 4.0 International License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution, and reproduction in any medium, provided you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. The Creative Commons Public Domain Dedication waiver (http://creativecommons.org/publicdomain/zero/1.0/) applies to the data made available in this article, unless otherwise stated.
Yun et al. BMC Anesthesiology (2016) 16:57
The first-attempt success rate of ProSeal™ LMA (PLMA) insertion and fiber-optic laryngeal score according to head position (sniffing, neck flexion and head extension by means of an 8-cm-high pillow vs. head extension without a pillow) and presence of a difficult airway were assessed [5]. The two factors (head position, difficult airway) had no influence on the first-attempt success rate of PLMA insertion and fiber-optic score in that study. In most clinical situations, with the exception of patients with cervical instability, the sniffing position has been used commonly, but the appropriate degree of head elevation has not been investigated thoroughly. The purpose of this study was to determine the pillow height (3 vs. 6 cm) that results in the highest success rate of LMA placement. The primary outcome variable was the success rate of PLMA insertion. The secondary outcome variables were blood on the surface of the PLMA cuff, postoperative sore throat and hoarseness as indices of complications.
Methods Patients and protocol
This prospective, single-center, randomized, single-blinded, parallel group comparison study was approved by the Institutional Review Board of the National Medical Center (authorization number H-1305/029-001). Written informed consents were obtained from all patients. This randomized controlled trial was registered at ClinicalTrials.gov (NCT02058030). Eighty adult patients (age range 18– 90 years; American Society of Anesthesiologists physical status 1–2) scheduled for minor surgery in the supine position were enrolled. The patients were recruited from November 2013 to November 2014. Patients were excluded if they had a known or predicted difficult airway, recent sore throat, mouth opening less than 2.5 cm, or risk of aspiration (non-fasted or gastroesophageal reflux disease). Anesthesiologists who did not perform the anesthesia enrolled the participants and assigned them to one of the two groups (3 cm group, 3 cm head elevation; 6 cm group, 6 cm head elevation), using a computer-generated randomization table (generated by Mi-Jung Yun at www.randomizer.org). The allocation ratio was 1:1. The assignment was concealed in an envelope until the start of anesthesia. Both patients and evaluators were blinded to the study. The standard anesthesia protocol was as follows: monitoring devices were connected before anesthetic induction; these included an electrocardiograph, pulse oximeter, gas analyzer and non-invasive blood pressure monitor. Anesthesia was induced with intravenous (IV) propofol (1–2 mg/kg) and inhalation of 6–8 vol% sevoflurane. Neuromuscular blockade was achieved with IV rocuronium (0.6 mg/kg). The patient’s head was elevated using a firm 3 cm pillow (3 cm group) or 6 cm pillow (6 cm group) and PLMA was inserted in the sniffing position.
Page 2 of 6
Anesthesia was maintained with 1.5–2.5 vol% sevoflurane in 50 % O2 and air. Water-based gel without a local anesthetic was applied to the posterior and lateral surface of the PLMA for lubrication, and the cuff was fully deflated before insertion. PLMA size was determined based on age and weight. Heart rate (HR) and mean blood pressure (MBP) were recorded 1 min before and 1 min after PLMA insertion. All insertions were performed by a single experienced PLMA user who was not blinded to the pillow height. The standard insertion technique was applied in both groups using an index finger, according to the manufacturer’s instructions [3]. The patient’s head was elevated with a pillow and the head was extended using the anesthesiologist’s non-dominant hand. The index finger of the dominant hand was placed in the retaining strap of the PLMA. The PLMA was pressed against the hard palate and advanced into the hypopharynx until resistance was felt. The laryngeal and oral axes were measured to assess their alignment. It was postulated that insertion would be more difficult with a greater difference in angle between the two axes and the PLMA would be more likely to buckle against the posterior pharyngeal wall. The laryngeal and oral axes were assessed using images obtained on the right side of the patient during PLMA insertion. A physician, who was blinded to the study, acquired the images while the pillow was covered using a barrier. The airway axes were defined as follows: angle of the ventral neck (an imaginary line along the long axis of the trachea) and the oral axis (an imaginary midline perpendicular to the line between the upper and lower lip). The angles were measured in images of all patients. Using a protractor, each angle was assessed three times by three individual anesthesiology residents, who were blinded to the study and could not determine pillow height on the images. The difference in angle of adjacent two axes was considered the alignment between the two axes. A lesser angle difference (oral axis - ventral neck angle) indicated greater alignment of the two airway axes (Fig. 1). The PLMA was connected to a breathing circuit after insertion, and the cuff was inflated with air until an effective airway was secured. An effective airway was defined as normal thoracoabdominal movement and a square-wave capnograph tracing. Airway pressure and end-tidal CO2 concentration were monitored. If insertion failed after two attempts using a pillow of the same height (head elevation), a third insertion trial was performed using a pillow height of the opposite group. If the third attempt was unsuccessful, it was regarded as a failure, and tracheal intubation was performed. The number of insertion attempts was recorded. Airway seal pressure was measured by setting the adjustable pressure limiting valve to 30 cmH2O and manually ventilating the
Yun et al. BMC Anesthesiology (2016) 16:57
Page 3 of 6
Fig. 1 Flow diagram generated in accordance with CONSORT 2010 guidelines
patient while listening with a stethoscope over the mouth [6] and epigastrium [7] to detect oropharyngeal and gastric air leaks, respectively. The PLMA was repositioned if air leaked up the drainage tube or if ventilation was ineffective (expired tidal volume
